The present invention relates to an electrical box assembly for housing non-metallic sheathed cables as well as a clamping device for holding the cables in place within an electrical box. The electrical housing assembly provides a more efficient structure for retention of cables without damaging the outer non-metallic sheath of the cables stored in the electrical box.
Electrical cables with non-metallic sheaths are generally housed in electrical boxes and squeezed between a surface of a clamp and an opposing surface of the electrical box. The clamp is generally tightened by a screw. Both the clamp and/or the box may contain an active surface coming in contact with the sheath of the cable.
The active surface of the box and/or the clamp may include embossments or like projections. Embossments are generally relief portions of the surface which are raised in the direction of the cable. Typically the height of the embossment exceeds or is very close to the thickness of the outer sheath of the cable. Examples of an electrical box with such embossments can be seen on the back wall of the electrical box in U.S. Patent No. 4,316,999 and on a curved surface of a spring finger in U.S. Patent No. 2,556,977.
When a clamp is tightened to a surface containing these embossments however, the outer sheath of the cable may be damaged due to the pressure of the clamping force on the electrical wires. The relief portions of the embossments may pierce the surface of the non-metallic sheath, thereby damaging the electrical cables.
The clamp is typically a planar clamp tightened against a wall of the box to secure electrical cables therein. The clamp is typically tightened with a torque in the range of approximately 10-35 inch-pounds, but may be more or less depending upon the circumstances. This pressure, in combination with the embossments and the flat shape of the clamp provide a hostile environment for the sheathed cables and often lead to damaged cables and results in improper electrical connections.
To provide a better clamping system in electrical boxes, it has been attempted to use a clamp with a curved surface in order to clamp electrical cables to an opposed surface. U.S. Patent No. 3,084,958 to Appleton and U.S. Patent No. 3,676,571 to Rubenstein both employ curved clamp structures in order to store electrical cables. In Appleton, a clamp assembly including an arched structure includes a jaw having a pair of integral arcuate shoes for engaging the cable or conduit and a stiffening wing disposed at an obtuse angle to the plane of the shoes. Each of these jaws is located at the end of the clamping structure. The Rubenstein reference similarly contains an arch structure which is used to restrain a cable against an opposed wall of an electrical box. The curved portions of the brackets however, merely serve to center the cable in the bracket when pressure is applied to the opposed surface of the electrical box. Each of these electrical cable boxes with curved surfaced brackets, however, fails to provide adequate gripping members for the cable.
U.S. Patent No. 2,556,977 to Paige discloses spring fingers with a curved surface used to store electrical cables in a box. The outer convex surface of the fingers further contains serrations which are used as gripping members for the electrical cable. While the serrations on the convex surface of the fingers in Paige are somewhat of an improvement over the prior art, they still do not provide an adequate fit for electrical cables in the box construction, as the convex surface of the fingers do not naturally xe2x80x9chugxe2x80x9d cables as a concave surface does. Furthermore, the spring member in Paige resiliently presses against the electrical cables to provide the compressive force to store the cables. It is desirable to provide a clamping system with a separate fastener to more easily control the compressive force storing the cables.
As mentioned above, the embossments of the prior art suffer from several deficiencies. The deficiencies are especially apparent when the embossments are used in conjunction with a compressive force which is necessary to store electrical cables, particularly cables with an outer non-metallic sheath. The compressive force in combination with the height of the embossments leads to damage to the cables.
It is desirous therefore to provide an electrical housing assembly for storing cables therein with a clamp system which is capable of storing electrical cables with a compressive force without damaging the cables.
It is desirous therefore to provide an electrical box for properly housing sheathed electrical cables. The electrical box desirably provides a snug fit for the electrical cables, including providing for the ability to clamp the electric cables with the proper force while not penetrating or damaging the sheath of the electric cable.
It is also desirous to provide an electrical box with improved serrations for gripping sheathed electrical cables stored therein. It is especially desirous to provide a gripping element less likely to pierce the cable sheathes.
The present invention also seeks to provide a more efficient clamp configuration to provide for proper storage of electrical cables. It is especially desirous to provide a clamp configuration which allows the proper torque force to clamp the electrical cables and not damage the cables.
An electrical housing assembly for supporting non-metallic sheathed electrical cables therein is provided. The housing assembly has an electrical box having a bottom wall with side walls projecting therefrom. The bottom and side walls define an open faced interior for receipt of one or more sheathed electrical cables therein. A clamp is additionally provided within the electrical box. The clamp structure is used for clamping non-metallic sheathed cable to an opposed surface of the box. The cable clamp has an arched surface including serrations thereon. The serrations are intended to engage the sheathed cable. The cable clamp structure provides a snug-fit for sheathed cables between the arched clamp and the bottom wall with the use of a fastener which secures the clamp to an opposed surface of the box to thereby securely hold one or more cables between the clamp and the opposed surface.
In another embodiment of the present invention an electrical housing assembly for supporting sheathed electrical cables is provided. The housing assembly is made up of an electrical box comprising a bottom wall with serrations for engaging the sheathed electrical cables. The bottom wall also has side walls projecting therefrom. A cable clamp is also provided for clamping non-metallic sheathed electrical cable. The cable clamp is an arched clamp with an opening therethrough. A fastener, preferably a screw, extends through the clamp opening and fastens the clamp to the bottom wall.
In a further embodiment of the present invention, an electrical housing assembly for supporting non-metallic sheathed electrical cables therein is provided. The housing assembly has an electrical box comprising a bottom wall with side walls projecting therefrom defining an open faced interior for receipt of one or more sheathed electrical cables. A clamp is used in conjunction with the electrical box for clamping at least one non-metallic sheathed cable to an opposed surface of the box. The clamp has an arched surface including serrations thereon for engagement with the sheathed cable or cables. A fastener is further provided for securing the clamp to an opposed surface of the box. The opposed surface of the box used in conjunction with the clamp includes serrations in order to securely hold the sheathed cable between the clamp and the opposed surface of the box.
In a still further embodiment of the present invention a cable clamp for securing at least one sheathed non-metallic electrical cable is provided. The cable clamp is preferably used in combination with an electrical box and a fastener to secure the cable to the electrical box. The cable clamp has an arched surface with serrations on a concave side of the arched surface.